I don't have a lot of patience for people getting all mystic about ki. No, there's not some mysterious fifth force undiscovered by scientists but available to martial artists.

I also don't have a lot of patience with people claiming that there's nothing to ki and similar imagery. Every athletic endeavor has their imagery which makes no sense logically, but helps the body move the right way for that situation. Weightlifting--the antithesis of internal arts in a lot of ways--certainly has lots.

And I appreciate the Sonnen quote, but five minutes on google would give me plenty of quotes from well-respected fighters talking about the importance of attitude and intent, which are certainly not measurable in the scientific sense. Even our own Keith talking about the OODA loop doesn't fit in that framework.

Perhaps all ki is is a way to use the mind to organize the body to deliver power that isn't dependent on muscular strength. If so, that's an explanation of why it is relevant, not a proof of why it is not.